1. Field of the Invention
The present invention relates to a coil component structured in such a way, among others, that a helical coil is covered with a magnetic body.
2. Description of the Related Art
Coil components (so-called “inductance components”), representative examples of which are inductors, choke coils and transformers, are structured in such a way that a helical coil is covered with a magnetic body, an insulating covering conductive wire is wound around a magnetic body, or the like. For the magnetic body covering the coil, Ni—Cu—Zn ferrite and other ferrites (=ceramics whose main constituent is iron oxide) are generally used.
In recent years, there has been a demand for coil components of this type offering electrical current amplification (=higher rated current) and, to meet this need, switching the material for the magnetic body from conventional ferrites to Fe—Cr—Si alloy is being examined (refer to patent Literature 1).
This Fe—Cr—Si alloy has a higher saturated magnetic flux density than conventional ferrites, but its volume resistivity is much lower than conventional ferrites. In other words, to switch the material for magnetic body from conventional ferrites to Fe—Cr—Si alloy for a coil component of the type where the helical coil is directly contacting the magnetic body, such as a coil component of the laminated type or the powder-compacted type, an ingenious idea is needed to bring the volume resistivity of the magnetic body itself, which is constituted by Fe—Cr—Si alloy grains, closer to the volume resistivity of the magnetic body constituted by ferrite grains, or preferably increase the volume resistivity of the former beyond that of the latter.
In essence, without ensuring a high volume resistivity of the magnetic body itself which is constituted by Fe—Cr—Si alloy grains, the saturated magnetic flux density of the material cannot be utilized to increase the saturated magnetic flux density of the component and, due to the phenomenon of current leaking from the coil to the magnetic body and disturbing the magnetic field, the inductance of the component itself will drop.
Note that Patent Literature 1 mentioned above discloses a method for manufacturing a magnetic body for coil component of the laminated type, which comprises laminating a magnetic body layer formed by a magnetic paste containing Fe—Cr—Si alloy grains as well as a glass component, with a conductor pattern, baking the laminate in a nitrogen atmosphere (=reducing atmosphere), and then impregnating the baked laminate with a thermo-setting resin.
However, this manufacturing method allows the glass component in the magnetic paste to remain in the magnetic body, and this glass component in the magnetic body reduces the volume ratio of Fe—Cr—Si alloy grains, which in turn lowers the saturated magnetic flux density of the component itself.
Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.